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1998 V70R Random Misfire Topic is solved

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

Mriv1998
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Re: 1998 V70R Random Misfire

Post by Mriv1998 »

Interesting... I will definitely check this out and hopefully see some positive results. If not I’m coming back to this chat lol
Mriv1998
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Re: 1998 V70R Random Misfire

Post by Mriv1998 »

The only codes I have at this moment are the SAS code and a misfire cylinder 1 code. The SAS code has been there for Quite a while and the misfire is the one that’s on and off and come in the form of different codes either as a random misfire or a misfire in a specific cylinder, OR a combination of BOTH. It’s very frustrating
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Re: 1998 V70R Random Misfire

Post by matthew1 »

A few things off the top of my head:

Plugs gapped, seated
Plug wires on and seated
Rotor clean, contacts good
No arching (check at night)
Fuel pressure good
MAF good
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1997 850 T5, MSD ignition coil, Hallman manual boost controller, injectors, R bumper, OMP strut brace [gone]
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Mriv1998
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Re: 1998 V70R Random Misfire

Post by Mriv1998 »

Thanks for the help guys I will certainly check all of these things... also would a fuel filter be something to check? I see them as part of many tune up kits and couldn’t tell you if mine was ever changed previously
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Re: 1998 V70R Random Misfire

Post by matthew1 »

You need air, fuel and spark. You're missing one of them in one cylinder. It's not air.

Fuel or spark... if you get a good fuel psi at the rail -- I think it's 45 or so, someone please chime in -- then it's spark. Just go buy a fuel pressure gauge, they're not expensive and checking it is simple.

Good fuel pressure doesn't mean your fuel filter doesn't need replacing, but it does mean the filter is not part of this problem.
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1997 850 T5, MSD ignition coil, Hallman manual boost controller, injectors, R bumper, OMP strut brace [gone]
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fitz548
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Re: 1998 V70R Random Misfire

Post by fitz548 »

Hello, i had this issue with my car a 1998 Volvo v70xc my car ran great but had this random misfire issue all of the codes like PO300/PO301/PO304/PO305 it drove me bat shit crazy trying to figure this nonsense out i replaced a whole bunch of stuff too plug/rotor/cap/wires/factory Bosch coil/vacuum lines. still had misfires. checked fuel pressure and it was very low 25 psi at idle it should be around 43psi at idle i had replaced the fuel pump in this car 3 years ago with a Volvo unit and it didn't last. so i replaced the fuel pump again along with the fuel filter and guess what the stupid misfires came right back- it drove me crazy then i started reading about this issue on many forums and i replaced 2 things and the misfires completely dissapeered and have never returned i replaced the fuel pump relay because the solder points inside the unit crack and fall apart after so many years and its a good idea to replace it if its the original. the second item i replaced was the crankshaft position sensor eventhough most of the time when these crank sensors go out there will be a check engine code i had a mechanic friend of mine look at my car and he told me there has only been a few times that he has seen these sensors go out without throwing a code but it does happen and these things ware out. ever since i replaced those two items my wagon is back to normal i romp on it daily and there is never a hiccup.
Mriv1998
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Re: 1998 V70R Random Misfire

Post by Mriv1998 »

Hey thanks for the info! I had read about those two parts in other threads but was unsure bc the codes I have didn’t match those items. At this point I cleared my cel twice in the past week and it’s been coming up as a cylinder one misfire only. I’m bringing my car to the Volvo mechanic this week to have the pcv re done and also to have this diagnosed. I’m going to bring up all the issues from this thread and hopefully this is the last time I have to deal with any misfires for a while. I love this car a lot but the misfire issue is driving me nuts
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Re: 1998 V70R Random Misfire

Post by abscate »

Try swapping plugs 1 and 2 and seeing if you can move the problem

New parts can be defective in funny ways, I happened to have a new plug fail in one week last fall.
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Mriv1998
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Re: 1998 V70R Random Misfire

Post by Mriv1998 »

Last month when I brought it to my mechanic (because I was over looking at it myself) he told me he had swapped injectors and moved around plugs. That’s when he told me my coil and coil module were bad and he had changed it for me. At that time I had the random code and after he fixed it the car drove fine for about a month until recently when the car started misfiring Again. This time it’s only cylinder 1 but as I said it really happens when I hit 60 at 3k rpm. This is why I’m so confused by the whole thing. Don’t want to keep paying for different things that won’t fix it
Mriv1998
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Year and Model: 1998 V70 R
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Re: 1998 V70R Random Misfire

Post by Mriv1998 »

So you’re saying I should check the plugs again by swapping?
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